1. Field of the Disclosed Subject Matter
The disclosed subject matter is related to the field of intravascular medical devices. More particularly, the presently disclosed subject matter relates to a multilayer balloon for a catheter.
2. Description of Related Subject Matter
Balloon catheters are used for a variety of treatments and techniques for intralumenal indications throughout the body, including the cardiovascular and peripheral systems. One such method is known as a percutaneous transluminal coronary angioplasty (PTCA) procedure. For purpose of example, in PTCA procedures, a guiding catheter is advanced until the distal tip of the guiding catheter is seated in the ostium of a desired coronary artery. A guidewire is then advanced out of the distal end of the guiding catheter into the patient's coronary artery until the distal end of the guidewire crosses a lesion to be dilated. A dilatation catheter having an inflatable balloon on the distal portion thereof is advanced into the patient's coronary anatomy, over the previously introduced guidewire, until the balloon of the dilatation catheter is properly positioned across the lesion. Once properly positioned, the dilatation balloon is inflated with liquid or suitable inflation medium one or more times to a predetermined size at relatively high pressures (e.g. greater than 8 atmospheres) to compress the stenosis against the arterial wall and thus open the passageway. Generally, the inflated diameter of the balloon is approximately the same diameter as the native diameter of the body lumen being dilated so as to complete the dilatation but not overexpand the artery wall. After the balloon is finally deflated, blood flow resumes through the dilated artery and the dilatation catheter can be removed therefrom.
In such angioplasty procedures, there may be restenosis of the artery, i.e. reformation of the arterial blockage, which necessitates either another angioplasty procedure, or some other method of repairing or strengthening the dilated area. To reduce the restenosis rate and to strengthen the dilated area, physicians frequently implant an intravascular prosthesis, generally called a stent, inside the artery at the site of the lesion. Stents can also be used to repair vessels having an intimal flap or dissection or to generally strengthen a weakened section of a vessel. A balloon-expandable stent is delivered to a desired location within a coronary artery in a contracted condition on a balloon of a catheter and then expanded to a larger diameter by expansion of the balloon. The balloon is deflated to remove the catheter with the stent remaining in place within the artery at the site of the dilated lesion.
In the design of catheter balloons, balloon characteristics such as strength (e.g., rupture pressure), flexibility, and compliance are tailored to provide the desired performance for a particular application. In stent applications, additional performance characteristics including stent retention, shredding and pin hole resistance, stent dislodgement force, and refold after stent deployment are also considered. Angioplasty and stent delivery balloons preferably have high strength (i.e., high rupture pressure) for inflation at relatively high pressure, and high flexibility and softness for improved ability to track the tortuous anatomy and cross lesions. The balloon compliance, which depends on factors such as the nature of the balloon material, the balloon wall thickness, and processing conditions, is established to provide the balloon with the desired amount of expansion during inflation. Compliant balloons, for example balloons made from materials such as polyethylene, exhibit substantial stretching upon the application of tensile force. Noncompliant balloons, for example balloons made from materials such as PET, exhibit relatively little stretching during inflation, and therefore provide controlled radial growth in response to an increase in inflation pressure within the working pressure range. However, noncompliant balloons generally have relatively low flexibility and softness. As such, it is difficult to provide a low compliant balloon with high flexibility and softness for enhanced catheter trackability.
As such, there is a need for a catheter balloon with high strength and limited compliance, yet with excellent ability to track within the patient's vasculature and cross lesions therein. Likewise a balloon having good stent retention, shredding and pin hole resistance, stent dislodgement force and refold after stent deployment is needed for stent applications. The disclosed subject matter satisfies these and other needs.